displaying background image within loop and if statement wordpress

Im having trouble displaying my background image.

I have created a loop to display my posts and then trying to set background image, however it's breaking somewhere? Below is my code within the loop.

<div class="artist-feed">
<?php
    $artistloop = new WP_Query( array( 'post_type' => 'artist') );
    if ( $artistloop->have_posts() ) :
        while ( $artistloop->have_posts() ) : $artistloop->the_post(); ?>

                <a href="<?php the_permalink(); ?>">
                  <div class="single-artist" style="background-image: url(<?php echo the_post_thumbnail(); ?>);">
                    <div class="artist-info">
                        <h2><?php echo get_the_title(); ?></h2>
                    </div>
                  </div>
                </a>
        <?php endwhile;
      endif;
  wp_reset_postdata();
?>
</div>

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